Source: Ontario Ministry of Agriculture, Food and Rural Affairs
What Is It?
Marbling is viewed as the major determinate of quality grades. It is the term applied to visible specks and streaks of fat in a cross section of the rib eye muscle. The chilled carcass is ribbed (cut) between the 12th and 13th ribs and the grader evaluates the cut surface for marbling, assigning a score. The quality grades (lowest to highest) are A, AA and AAA with a few carcasses receiving the designation Prime.
Marbling is a moderately heritable beef cattle trait. By selecting for it we can increase or decrease the level of marbling found in future generations of cattle. The talk and actions of the industry the past couple of years has focused on increasing marbling to ensure product quality, but will it?
What Do We Know from Research?
Marbling is our best indicator, to date, of eating quality when grading beef carcasses. Higher levels of marbling have been associated with increased tenderness, juiciness and flavour of beef. Research in the U.S. has indicated that USDA Select (equivalent to Canada AA) is the minimum marbling grade to ensure acceptable eating quality for most consumers. However, there is so much overlap in palatability amongst the grades you can have steaks from Prime and A grade carcasses that are equally palatable. Marbling accounts for only 15% of the variation in tenderness. Tenderness is the major industry issue with one in five steaks considered tough.
Where Does that Leave Producers?
Marbling is the best option we have to date to measure eating quality of beef and with appropriate genetics and proper nutrition we can achieve the levels desirable for today’s market.
Selecting for Marbling in the Beef Herd
Selection decisions placing more emphasis on a trait must ensure continued maternal function and efficiency of the cow herd. The impact of selection for marbling on beef cow production traits has not been widely researched. The available research indicates little relationship (positive or negative) between marbling and measures of reproduction, milk production, preweaning growth, feedlot performance, external fat deposition and mature size.
However, the researchers concluded that single-trait selection for marbling would be ill advised; as would single trait selection for any beef cattle production trait. The solution lies with multiple trait selection based on expected progeny differences (EPDs). These traits would include measures of reproduction, growth, maternal and carcass characteristics.
When making any selection decisions you should ensure your cow herd has maternal function and efficiency, matching your environment and resources. Primarily selecting for carcass characteristics will not achieve acceptable maternal function but superior carcass characteristics can be achieved without negatively effecting maternal function, depending on sire choice. The use of terminal sires (all calves marketed) allow breeders to focus their selection on carcass traits, including marbling, without the threat of losing the maternal producing ability of their cow herd.
There is an optimum for everything we do; selection for marbling will not negatively effect profitability of your herd if other traits are kept in balance.
Author: Joanne Handley – Beef Cattle Geneticist/OMAFRA